This invention is an improvement on an earlier invention disclosed in copending application Ser. No. 756,358 of Henry I. Smith for Enhancing Epitaxy and Preferred Orientation, now U.S. Pat. No. 4,333,792, granted June 8, 1982, and relates, in general, to improving the crystallographic quality of solid films grown on surfaces of solid substrates, and more particularly, to improved means for obtaining epitaxial or preferred orientation films on solid substrates, both crystalline and amorphous.
Much of modern technology makes use of thin solid films on the surfaces of solid substrates. Epitaxial and preferred orientation films are particularly important, notably in microelectronic devices, thin film optical devices and solar cells. Thus, improved methods of preparing epitaxial and preferred orientation films are of great importance.
The principle involved in the earlier invention, referenced above, was to use a plurality of artificial defects, formed at predetermined locations at the surface of a solid substrate, to determine, control or influence, by means of the geometric arrangement of adjacent defects, the crystallographic orientation of a film deposited at said surface. The said artificial defects were either (1) artificial point defects or (2) artificial surface relief structure. The method disclosed in said earlier patent has been named "graphoepitaxy" (see "Crystallographic Orientation of Silicon on an Amorphous Substrate Using an Artificial Surface Relief Grating and Laser Crystallization", by M. W. Geis, D. C. Flanders and H. I. Smith, in Applied Physics Letters, Vol. 35, pp. 71-74, July 1, 1979). The name is derived from the Greek ("grapho" meaning to write or incise) and was chosen to convey the principle of using an artificially created surface pattern to induce epitaxy. In addition to the aforesaid copending application Ser. No. 756,358) two additional copending applications disclose improvements on the graphoepitaxy process. These copending applications are entitled "Improving Graphoepitaxy", by M. W. Geis, D. C. Flanders and H. I. Smith, Ser. No. 43,541 filed May 29, 1979, now abandoned, and "Three Dimensional Integration by Graphoepitaxy", by H. I. Smith, D. C. Flanders and M. W. Geis, Ser. No. 43,389 filed May 29, 1979, now abandoned. The present invention concerns (1) the use of a cover or "cap" of material over a film to be oriented; (2) the use of such a cap over a film to be oriented wherein the film is formed into discrete islands or stripes; (3) the use of such a cap over a film to be oriented wherein the substrate on which the film is located has artificial surface relief structure formed in it; (4) the use of such a cap over a film to be oriented wherein the cap has artificial surface relief structure formed in it; (5) the use of such a cap over a film to be oriented wherein both the substrate and the cap have artificial surface relief structure formed in them; (6) the use of a cap over a film to be oriented in any of the above configurations together with heating of the film by irradiation with electromagnetic radiation.